What weather details actually belong in a spray record?

Wind speed and direction at the moment of application, temperature, and relative humidity, recorded at the sprayer, not estimated afterward. Some labels also constrain application under temperature inversion conditions, in which case that assessment belongs in the record too. The goal is a snapshot of the atmosphere at the exact time the boom was down, not a general sense of what the day was like.

Why does wind direction matter as much as wind speed?

Because a drift complaint is almost always about where the material went, not just whether conditions were calm enough to spray. A low wind speed blowing steadily toward a sensitive neighboring crop can be more consequential than a higher speed blowing away from anything nearby. Speed alone answers whether the label's ceiling was respected; direction is what tells you, and eventually a claimant, whether your field is the plausible source.

Does the label actually set wind or weather limits for spraying?

Many labels do, in the form of maximum wind speeds, buffer distances from sensitive areas, or restrictions during temperature inversions, and those limits are set by the label and enforced by your regulator — not by this page or by general practice. Whether a specific limit applies to a specific product is a question for that product's label, read at the time of application.

What if a complaint arrives weeks after the application?

This is the normal timeline for a drift complaint — the affected crop often shows symptoms days or weeks after exposure, by which point the field has moved on to other work and memory of the exact conditions has faded. A weather field recorded at the time of application is the only version of that information that still exists intact by the time anyone asks the question.

Drift Complaints and the Weather Field

Ask to see a working spray record from almost any farm and the gap is nearly always in the same place. The product is filled in. The rate is filled in. The date is filled in. The line for wind — speed, direction, anything about the atmosphere at the moment the boom went down — is blank, because the crop needed spraying and nobody paused to look at a flag or check an app before starting the pass.

That blank line is where a drift complaint lives. Nobody disputes that a field was sprayed; the entire question, when a neighbor's crop shows injury, is what the conditions were at the time — and a record with no weather field has no answer to give. This page is about why that one field is the most consequential thing most spray records omit, and what it takes to actually capture it.

The label is the authority. This page does not state a wind speed limit, a buffer distance, or any other weather threshold for any product, and you should distrust anything that does. Those limits, where they exist, are set by the product label and enforced by your regulator, and they vary by product and jurisdiction. What follows is about the process of recording the weather at application — not a substitute for reading the label of the product you are actually using.

A drift complaint is a question about a specific moment

When a neighboring crop shows unexplained injury, the investigation that follows does not ask what usually happens on your farm. It asks what happened at the specific hour a specific pass went down — which direction the wind was blowing, how hard, what the temperature and humidity were, whether conditions were inside whatever limits the label set. Everything else about the application can be perfect and still leave that one question unanswered if nobody wrote down the weather.

This is what makes the weather field different from most of the rest of a spray record. The product, the rate, the field, the date — all of those can be reconstructed after the fact from an invoice, a tank log, or a memory that's still fairly fresh. The weather at a specific hour cannot be reconstructed at all. Once the moment passes, that information exists nowhere except in a note taken at the time, or it doesn't exist.

Direction answers a different question than speed does

It is common to record wind speed and skip direction, on the logic that speed is what the label restricts. But speed and direction answer two different questions, and a complaint usually needs both. Speed tells you whether the application respected whatever ceiling the label sets. Direction tells you where the material was actually headed — and a claim of drift onto a specific neighboring field lives or dies on whether the wind, however fast, was blowing that way at all.

A record with speed but no direction can show the application was within limits and still be unable to say whether your field is even a plausible source of a specific complaint. A record with both can settle the question outright — sometimes in your favor, by showing the wind was blowing away from the affected crop the entire time. Recording direction is not extra caution. It is the field that actually resolves the dispute.

Recorded at the sprayer, it's evidence; reconstructed later, it's a guess

The honest test of a weather field is whether it was written down while the wind was actually blowing, or assembled afterward from memory once a complaint arrived. The two look identical on paper and are worth completely different amounts. A number written at the time is evidence a hostile party has to take seriously. A number reconstructed a week later — "it was calm, I remember" — is a guess dressed as a record, and it will be read as one by anyone with a reason to doubt it.

The fix costs seconds: check a handheld anemometer or a phone weather app, note the wind speed and direction, the temperature, and the humidity, before or during the pass, on the same document as the product and the rate. It is the cheapest field in the entire record to fill in and the most expensive one to have missing, which is exactly why it's the one most often skipped — nothing about the day of the spray makes it feel urgent, and a field that never causes a problem never teaches anyone that the habit was worth keeping. The habit only proves its worth on the one afternoon, out of a hundred routine passes, when a neighbor calls.

The record that protects you is the same one that could implicate you

It's worth being honest about what a complete weather field does in both directions. If conditions were genuinely within the label's limits and the wind was blowing away from the affected area, the record clears you, cleanly, without argument. If conditions were marginal — wind higher than it should have been, blowing toward a sensitive crop — the same record documents that too.

This is not a reason to skip recording it. A field with no weather data does not protect an operation that sprayed in bad conditions; it just removes the evidence either way, and an investigator or a neighbor's attorney will read a missing field as an absence of candor, not an absence of wrongdoing. The record that actually protects a farm is the complete one, made before anyone had a reason to want it to say anything in particular.

Where this sits in the rest of the record

The weather field is one line among many in the same document described in what belongs in a spray record, and it deserves its own page only because it is the field farms skip most and the one a complaint turns on most directly. It matters in the same way for a tank-mix pass or a custom-applied pass — the atmosphere doesn't care who mixed the tank or drove the sprayer.

Farm40 lets you export any block or field's application history as a CSV, including whatever weather detail you entered against each pass, which is useful when a complaint arrives and you need the season's record in front of you quickly. Its limit is the one that matters most here: an export is only a view of what was actually entered at the time. If the weather line was left blank on the day of the spray, the export will faithfully show a blank line — it cannot retroactively tell you what the wind was doing. The record has to be made complete at the sprayer. Nothing downstream can fix a gap left there.

Frequently asked questions

What weather details actually belong in a spray record?: Wind speed and direction at the moment of application, temperature, and relative humidity, recorded at the sprayer, not estimated afterward. Some labels also constrain application under temperature inversion conditions, in which case that assessment belongs in the record too. The goal is a snapshot of the atmosphere at the exact time the boom was down, not a general sense of what the day was like.
Why does wind direction matter as much as wind speed?: Because a drift complaint is almost always about where the material went, not just whether conditions were calm enough to spray. A low wind speed blowing steadily toward a sensitive neighboring crop can be more consequential than a higher speed blowing away from anything nearby. Speed alone answers whether the label's ceiling was respected; direction is what tells you, and eventually a claimant, whether your field is the plausible source.
Does the label actually set wind or weather limits for spraying?: Many labels do, in the form of maximum wind speeds, buffer distances from sensitive areas, or restrictions during temperature inversions, and those limits are set by the label and enforced by your regulator — not by this page or by general practice. Whether a specific limit applies to a specific product is a question for that product's label, read at the time of application.
What if a complaint arrives weeks after the application?: This is the normal timeline for a drift complaint — the affected crop often shows symptoms days or weeks after exposure, by which point the field has moved on to other work and memory of the exact conditions has faded. A weather field recorded at the time of application is the only version of that information that still exists intact by the time anyone asks the question.